Building Technology 2: Wood Framing Systems PDF

Building Technology 2 Wood Framing Systems  Introduction Wood Framing Systems Light Wood Framing Lecture Outline Introduction  Wood is man’s earliest building material, first used during the Neolithic period Used for shelter (in stockade construction) and fortification (i...

Building Technology 2 Wood Framing Systems  Introduction Wood Framing Systems Light Wood Framing Lecture Outline Introduction  Wood is man’s earliest building material, first used during the Neolithic period Used for shelter (in stockade construction) and fortification (in palisade construction) Development Timber construction Braced frame construction Light framing construction Introduction  Key reasons for using wood as a construction material Strength and versatility Renewability and sustainability Insulation and energy efficiency Ease of construction Aesthetic appeal Seismic and earthquake resistance Low embodied energy Local availability Natural acoustic and thermal insulation Introduction  Prominence in use Today, wood is the primary choice of building material in building homes in the US and the UK Reasons behind the prominence Traditional building practices Abundance of forest reserves Flexibility in design Cost-effectiveness Regulatory support Do-it-yourself culture Introduction  Prominence in use In the Philippine setting, wood is not the primary choice of building material for homes, especially in urban areas Reasons behind the unpopularity Climate and environment Building regulations Cultural and societal factors Cost and availability Sustainability Introduction  Prominence in use Due to their extensive use, traditional building practices from the US and the UK have gradually developed and used until today Introduction Wood Framing Systems  Broadly classified into two: heavy wood framing and light wood framing systems Heavy wood framing system Also known as post-and-beam framing, beam-and-girder framing, and timber framing A wood framing system, predating light wood framing system, that utilizes heavy timber, squared-off and carefully fitted and jointed, with joints secured by large wooden pegs Half-timbered: a building whose structural frame of timber is left exposed on the exterior, in many cases the infill between timbers will be used for decorative effect Floor joists are carried by girders, and roof trusses or rafters by girts, which frame into posts; studs rest on floor sills and extend up the girder or girt in every floor Type of framing used in the Philippines Wood Framing Systems  Heavy wood framing system Wood Framing Systems  Heavy wood framing system Joints originally uses lap jointing, then later pegged mortise and tenon jointing Later joints utilizes steel connectors, such as bearing plates and column caps Wood Framing Systems  Heavy wood framing system Wood Framing Systems  Heavy wood framing system Braced framing An enhanced timber framing system designed to resist lateral loads, such as wind and seismic pressure Developed in the late Middle Ages Joints are mortised and tenoned Types: diagonal bracing, K-bracing, V-bracing, inverted V-bracing, and X-bracing Wood Framing Systems  Heavy wood framing system Braced framing Spaces in between members were filled either with brickwork, stone masonry, or wattle- and-daub construction Wood Framing Systems  Light wood framing system A wood framing system that utilizes many small and closely-spaced members, assembled by nailing The standard for the US suburban housing Further classified into three: balloon framing, combination framing, and platform framing Utilizes dimension lumber and/or engineered wood Recap: dimension lumber and engineered wood Dimension lumber Lumber cut to a predetermined standard dimensions Engineered wood A composite wood product made by binding or fixing wood components together with adhesives Wood Framing Systems  Light wood framing system 2xs and 4xs are considered dimension lumber. Oriented strand board (OSB), an engineered wood board Wood Framing Systems  Light wood framing system Engineered wood Glue-laminated wood Also called glulam wood Large wood structural members produced by joining smaller strips of wood with glue Major reasons to laminate: size, shape, and quality Seasoned before lamination to lower than the usual desired moisture content, 12% Most common individual laminations are 2 inches (50mm) nominally thick (1 ½ in/38 mm) Wood Framing Systems  Light wood framing system Engineered wood Glue-laminated wood Adhesives are chosen according to moisture conditions under the member is subjected to, and layers are oriented along the length of the lumber End joints are either scarf-jointed or finger jointed Wood Framing Systems  Light wood framing system Engineered wood Cross-laminated timber Abbreviated as CLT Structural panels laminated from solid lumber, specifically dimension lumber, each layer glued perpendicular to the previous Seasoned before lamination to lower than the usual desired moisture content, 12% Planed or sanded before assembly to ensure good wood-to-adhesive bonding During gluing, full stack is compressed in a hydraulic or vacuum press, then cured Wood Framing Systems  Light wood framing system Engineered wood Cross-laminated timber End joints are finger-jointed Made up of odd number of layers for a balanced structural behavior Common thickness range from 2 ¼ to 16 inches (57-400 mm), widths range from 4-15 feet (1220- 4500 mm), and lengths from 40-60 feet (12-18 m) Wood Framing Systems  Light wood framing system Engineered wood Structural composite lumber Abbreviated as SCL, and also called engineered lumber Product substitute for solid lumber and are made from wood veneers or wood fiber strands and glue Includes laminated strand lumber (LSL), oriented strand lumber (OSL), laminated veneer lumber (LVL), and parallel strand lumber (PSL) LSL and OSL are made from shredded wood strands, coated with adhesive, then pressed into a rectangular cross section, and cured under heat and pressure Difference: wood strands in LSL are longer than those in OSL Least strong and least expensive of the composite lumber products Used mainly for rim boards and short-span headers, and can’t be curved or stained Wood Framing Systems  Light wood framing system Engineered wood Structural composite lumber LVL is made from thin wood veneer sheets, as wide as the member is deep, that are glued and laminated into thicker members Has higher shear strength than LSL and OSL More expensive than LSL and OSL but more affordable compared to PSL and glulam PSL is manufactured using thin veneer panels cut into narrow parallel strips and then bonded together using a process similar to LSL and OSL The heaviest, strongest, and most expensive SCL Well-suited to applications where high bending or compression stress are needed, thus primarily used as long-span beams, columns and headers SCLs may be used as studs and posts, and are finger-jointed to achieve longer spans Wood Framing Systems  Light wood framing system Engineered wood Structural composite lumber Wood Framing Systems  Light wood framing system Engineered wood Wood I-joist Manufactured wood I-shaped members, consisting of top and bottom flanges, made from solid lumber, LSL or LVL, connected by a thinner web, either made from plywood or OSB Use wood more efficiently than conventional dimension lumber, being lighter in weight but can span farther between supports More dimensionally stable, lacks crooks and bows, and are available in lengths up to 40 feet (12.2 m) Wood Framing Systems  Light wood framing system Engineered wood Wood-plastic composite Abbreviated as WPC Made from blends of plastic with wood or agricultural fibers, usually in roughly equal proportions, heated and pressed, extruded, or injection-molded into final form May contain smaller quantities of ultraviolet stabilizers, pigments, lubricants and biocides Offer more consistent material quality, freedom from defects and distortion, and possibly superior resistance to moisture Used often for exterior decking, exterior railing systems, and finish trim, both interior and exterior WPC decking, made commonly from blends of polyethylene or polypropylene and wood fiber, is available in lengths up to 20 feet (6.1 m), and may be fastened with corrosion-resistant nails or screws or with concealed hardware Wood Framing Systems  Light wood framing system Engineered wood Wood-plastic composite Wood Framing Systems Light Wood Framing System  Light wood framing construction was the first uniquely American building system, developed in the early 19th century Development accelerated due to two technological breakthroughs Cheapening of wood boards and small framing members Cheapening of machine-made nails Balloon framing was the earliest wood framing system The lightest form of framing Features continuous lengths of studding and corner posts, running from sill to roof plate Quicker and faster to construct compared to timber framing Light Wood Framing  Balloon framing Light Wood Framing  Balloon framing Light Wood Framing  Balloon framing Issues encountered Full-length studs were too long to erect efficiently Tall, hollow spaces between studs acted as multiple chimneys in a fire, unless closed off with fireblocking Modified versions of the balloon framing were made to address the issues, but the most successful is the platform framing Light Wood Framing  Combination framing Combination Frame A modification of the braced frame More rigid than balloon framing Consists of lighter timber with less mortising and pinning to save material and labor Girts are framed into the corner posts to serve both as floor support and frame bracing Drop girts: girts supporting floor joists Raised/flush girts: girts running parallel to floor joists Uses diagonal bracing Light Wood Framing  Platform framing Also called Western framing Considered the universal standard for light wood frame construction Concept: floor platform before loadbearing walls Conventional construction entirely utilizes 2xs members (38 mm actual), ordered and cut to the nearest 2-foot length (600 mm) Members are arranged to fall on a 4-foot module (1.20 m), ensuring the use of standard wood panels (4x8 feet, 1.20x2.40 meters) for sheathing Light Wood Framing  Platform framing Advantages Uses short, easily-handled lengths of lumber for wall framing Fireblocking is naturally provided by floor platforms Platforms can be used as convenient working spaces Disadvantage Wood grain of the platforms run horizontally, susceptible to shrinkage Light Wood Framing  Platform framing Light Wood Framing  Platform framing Platform Frame. Light Wood Framing Fin